Ralston will start Saturday's game against Atlanta in Miami, Kevin Barral of FishonFirst.com reports.
The 29-year-old rookie right-hander will be making his first MLB start and his first start at any level of the professional ranks since 2022. Between his stops with Miami and Triple-A Jacksonville this season, Ralston hasn't tossed more than three innings, so he's unlikely to work more than once through the batting order Saturday before turning the game over to the Marlins bullpen.